Just got a refund today for the last missing item so everything is good now. The advice to tell them exactly what is missing in every e-mail is spot on.
Ordered: may 8th
Items shipped: may 10th
Partial Items received:May 28th
First partial refund (without asking):June 8th
Rest of refund received: June28th
Usually good service from these guys, but they should probably have a system to see if items are in stock to avoid mess ups like this.